Nerve stimulation (neurostimulation) technology includes applications such as electrical neuromodulation, functional electrical stimulation, and therapeutic electrical stimulation. Nerve stimulation is an effective clinical tool used to treat various chronic medical disorders and conditions. Examples include (1) deep brain stimulation (DBS) for treating Parkinson's disease and essential tremor, (2) spinal cord stimulation for pain and urinary dysfunction, and (3) peripheral nerve stimulation for overactive bladder, pain, obstructive sleep apnea, headache, migraine, epilepsy, depression, hypertension, chronic heart failure, and stroke rehabilitation. Peripheral nerves may include, for example, the vagus nerve, occipital nerve, cranial nerves, spinal nerves, pudendal nerves, cutaneous nerves, and the sciatic nerve.
Therapeutic efficacy of neurostimulation technology is attributed to selective activation of targeted tissue or neural circuitry. This is achieved by low recruitment of non-targeted tissue or neural circuit(s). Unintended activation of non-targeted nervous tissue, by a broad or incorrectly localized stimulation field, may deter therapeutic benefit. Unintended modulation of biological system(s) may also be due to, for example, inhibitory rather than, or in addition to, excitatory effects, or other unwanted activity or physiological responses. Unintended modulation may produce side-effects and outcomes that are contrary to the intended response.